Universal AC or DC Aircraft Device Power Supply Having Power Factor Correction
An aircraft device power supply is capable of connecting to either an AC or a DC power bus provided on an aircraft. When connected to an aircraft's AC power bus, an AC power signal is EMI-filtered, stepped down in voltage to the same voltage as that of the DC power bus, and then rectified. When connected to an aircraft's DC power bus, a DC power signal is EMI-filtered before it is merged with the rectified AC power signal via an AC/DC switchover subcircuit. The output of the AC/DC switchover subcircuit is input to a power factor correction subcircuit which outputs a boosted DC voltage, regardless of which of the AC or DC aircraft power buses is connected to the power supply. A step down converter reduces the boosted DC voltage to a lower, system voltage which may then be further reduced or modified, as appropriate for device to be powered.
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The present application claims priority to U.S. Provisional application No. 60/796,497, filed May 1, 2006, whose contents are incorporated by reference in their entirety.
FIELD OF THE INVENTIONOne embodiment of the present invention is directed to a power supply for aircraft-mounted devices. In particular, one embodiment is directed to a power supply that is configured to be connected to either 115 V AC or 28 VDC aircraft power bus, and outputs one or more predetermined DC voltages.
BACKGROUND INFORMATIONMany aircraft-mounted devices use either a 115VAC power bus or a 28VDC power bus, but not both. These devices include computers, display panels, communications equipment, control panels, sensors and the like. As is known to those skilled in the art, each such device includes a power supply that connects to one of the two aircraft power buses. The power supply in each such device then provides that device with one or more system voltages to power components such as fans, integrated circuit chips, indicators, transmitters, etc. within that device.
U.S. Pat. No. 4,100,596 and U.S. Pat. No. 4,103,325 disclose an aircraft power supply which takes in a single-phase AC voltage and a DC voltage, and outputs a three-phase AC voltage.
U.S. Pat. No. 5,49,187 discloses an aircraft power supply which senses whether the voltage is an aircraft AC voltage or an aircraft DC voltage and outputs a DC voltage.
U.S. Pat. No. 6,654,267 discloses an aircraft power supply which takes the regularly available 400 Hz 115 VAC power and converts into a DC voltage for use by passengers, e.g., 12 or 24 VDC. The power supply also converts 400 Hz AC to 60 Hz AC, and shapes the waveform.
U.S. Pat. No. 7,112,944 discloses an aircraft power supply having both AC and DC power source inputs to supply a variety of output voltages.
However, none of the above power supplies employ circuitry to correct the power factor and reduce harmonic distortion of a rectified AC current.
SUMMARY OF THE INVENTIONIn one aspect the present invention is directed to an aircraft power supply that can be connected to either an aircraft AC power source or an aircraft DC power source, to produce a DC system voltage for powering aircraft-mounted devices.
In one embodiment, such an aircraft power supply includes:
a first subcircuit having an input and an output, the first subcircuit configured to accept an AC power signal, convert the AC power signal to a lower voltage, and output a rectified AC power signal, when the power supply is connected to an aircraft AC power bus;
an AC/DC switchover subcircuit having a first input connected to the output of the first subcircuit and a second input, and further having a switchover output, the AC/DC switchover subcircuit configured to: output the rectified AC power signal, when the power supply is connected to the aircraft AC power bus and not to an aircraft DC power bus; and output a DC signal, when the power supply is connected to the aircraft DC power bus and not to the aircraft AC power bus;
a power factor correction subcircuit having an input connected to the switchover output, and further having an output, the power factor correction subcircuit configured to correct a power factor of a rectified AC power signal, when the power supply is connected to the aircraft AC power bus, and further configured to output a DC power signal having a first voltage; and
a DC-DC step-down converter having an input connected to the output of the power factor correction subcircuit, and further having a system voltage output, the DC-DC step-down converter configured to reduce the first voltage to a second voltage lower than said first voltage.
The power supply may include an AC electromagnetic interference (EMI) filter configured to output a filtered AC power signal to the input of the first subcircuit, when the power supply is connected to the aircraft AC power bus; and a DC EMI filter configured to output a filtered DC power signal to the second input of the AC/DC switchover subcircuit, when the power supply is connected to the aircraft DC power bus. The AC EMI filter may be configured to filter a 115V, 400 Hz power signal from the aircraft's AC power bus; and the DC EMI filter may configured to filter a 28 VDC power signal from the aircraft's DC power bus. The AC EMI filter and DC EMI filter may be provided on a common integrated circuit board.
In another aspect, the invention is directed to an aircraft-mountable device adapted to be connected to either an aircraft alternating current (AC) power bus or to an aircraft direct current (DC) power bus, the aircraft-mountable device having the aforementioned power supply. The aircraft-mountable device may be a computer, a display panel, communications equipment, a control panel, or a sensor.
The contents of aforementioned U.S. Pat. No. 4,100,596, U.S. Pat. No. 4,103,325, U.S. Pat. No. 5,49,187, U.S. Pat. No. 6,654,267 and U.S. Pat. No. 7,112,944 are incorporated by reference to the extent necessary to under the present invention.
Also in the typical case, the circuit 100 serves as the power supply for a device, the device itself for use in an aircraft and thus capable of being powered off of either the aircraft's AC power bus 102 or the aircraft's DC power bus 104. Thus devices such as computers, display panels, communications equipment, control panels, sensors or any one of a host of other powered devices may incorporate such a power supply circuit 100.
In one embodiment, the incoming power from the aircraft power buses is first subjected to (electromagnetic interference) EMI filtering. On the AC side, the aircraft's AC current comes in through a first pair of conductors 102H, 102L and enters a 115VAC, 400 Hz EMI filter 108 which is designed to filter power signals above 400 Hz. The output of the 115VAC 400 Hz EMI filter 108 is a filtered AC power signal across lines 142H, 142L. On the DC side, the aircraft's DC current comes in through a second pair of conductors 104H, 104L and enters a 28 VDC EMI filter 110 which is designed to filter power signals above the DC frequency. The output of the 28 VDC EMI filter 110 is a filtered DC power signal across lines 144H, 144L.
It can therefore be seen from the foregoing that the AC EMI filter 108 is configured to filter a 115V, 400 Hz power signal from the aircraft's AC power bus 102, while the DC EMI filter 110 is configured to filter a 28 VDC power signal from the aircraft's DC power bus 104. Though filtering the incoming power signals is highly advisable, it is not an absolute necessity. Furthermore, while the AC EMI filter 108 and DC EMI filter 110 are shown as separate filters, they may be located proximate one another in a common package 106 or on a common circuit board. It is understood that each pair of conductors 102H, 102L and 104H, 104L are at least partially incorporated into connectors which mate with complementary connectors attached to the power buses 102, 104.
While EMI filters 108, 110 are used in the embodiment shown in
The output of the AC EMI filter 108 on lines 142H, 142L is connected to the input of an AC power signal shaping subcircuit 112. The AC power signal shaping circuitry includes a 4:1 turns ratio AC transformer 114 followed by a full-wave rectifier 116 (see
The output of the AC power signal shaping subcircuit 112 is connected to an AC/DC switchover circuit 120, as is the output of the 28 VDC EMI filter. Thus, when the circuit 100 is connected to the aircraft's 115 VAC power bus 102, the rectified AC signal on lines 418H, 418L is input to the AC/DC switchover circuit 120. Similarly, when the circuit 100 is connected to the aircraft's 28 VDC power bus 104, the filtered DC signal on lines 144H, 144L is input to the AC/DC switchover circuit 120. The AC/DC switchover circuit 120 permits whichever of the rectified AC signal (on lines 418H, 418L) and the filtered DC signal (on lines 144H, 144L) is present, to pass on to the remainder of circuit 100 via AC/DC switchover output lines 428H, 428L.
As seen in
As seen in
As is the case with AC/DC switchover circuit 120a (
At the AC/DC switchover circuit, the voltage of the rectified AC power signal is approximately the same as a voltage of the filtered DC power signal so that the PFC subcircuit 122 receives approximately the same voltage, whether the power supply is connected to the aircraft's AC power bus or to the aircraft's DC power bus. The AC/DC switchover output lines 428H, 428L are connected to a power factor correction subcircuit 122 (“PFC subcircuif”). As is known to those skilled in the art, ideally, the power factor for converting a rectified power signal AC to DC should be 1.0. As its name indicates, power factor correction subcircuit 122 helps bring the power factor of the rectified AC signal to close to unity. It also helps reduce current harmonic distortion resulting from nonlinearities arising during the conversion. The PFC subcircuit 122 utilizes a standard DC-DC boost-converter topology to control the current drawn with respect to the aircraft power buses 102, 104, thus providing for power factor correction and current harmonic reduction.
The output of the PFC controller chip 250 on line 276 is applied to a transistor switch 256 (represented by transistors Q1 and Q2 in
Three main inputs are used in the control scheme of the PFC controller chip 250. First, the rectified AC signal on the high AC/DC switchover output line 428H, connected via line 244, is scaled 248, preferably via a voltage divider comprising a pair of resistors, and presented on line 272 to the AC input of the PFC controller chip 250. This allows a scaled version of the full-wave rectified AC signal input waveform to be used as a template from which the current waveform is modeled against. Second, the low AC/DC switchover output line 428L, from which the current shunt resistor 242 connects to ground (see
In the embodiment shown, the output 126H of the boost converter 630 from subcircuit 122 (see
In the embodiment shown, while the input voltage on line 126H is nominally between 60-90V, the output system voltage on line 130 from the subcircuitry 700 associated with the DC-DC step-down converter 128 is about 12 VDC. The 12 VDC output system voltage on line 130 from the step-down converter 128 can be further reduced and/or modified to produce desired DC voltages required by the various components (“component voltages”) within each device having a power supply in accordance with the present invention. This may be done by the use of DC-DC converters, shown generally as 140A, 140B in
Several embodiments of the present invention are specifically illustrated and/or described herein. However, it will be appreciated that modifications and variations of the present invention, especially electrical equivalents of the components in the specific implementations, are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.
Claims
1. An aircraft device power supply adapted to be connected to either an aircraft alternating current (AC) power bus or to an aircraft direct current (DC) power bus, and comprising:
- a first subcircuit having an input and an output, the first subcircuit configured to accept an AC power signal, convert the AC power signal to a lower voltage, and output a rectified AC power signal, when the power supply is connected to an aircraft AC power bus;
- an AC/DC switchover subcircuit having a first input connected to the output of the first subcircuit and a second input, and further having a switchover output, the AC/DC switchover subcircuit configured to: output the rectified AC power signal, when the power supply is connected to the aircraft AC power bus and not to an aircraft DC power bus; and output a DC signal, when the power supply is connected to the aircraft DC power bus and not to the aircraft AC power bus;
- a power factor correction subcircuit having an input connected to the switchover output, and further having an output, the power factor correction subcircuit configured to correct a power factor of a rectified AC power signal, when the power supply is connected to the aircraft AC power bus, and further configured to output a DC power signal having a first voltage; and
- a DC-DC step-down converter having an input connected to the output of the power factor correction subcircuit, and further having a system voltage output, the DC-DC step-down converter configured to reduce the first voltage to a second voltage lower than said first voltage.
2. The aircraft device power supply according to claim 1, further comprising:
- an AC electromagnetic interference (EMI) filter configured to output a filtered AC power signal to the input of the first subcircuit, when the power supply is connected to the aircraft AC power bus; and
- a DC EMI filter configured to output a filtered DC power signal to the second input of the AC/DC switchover subcircuit, when the power supply is connected to the aircraft DC power bus.
3. The aircraft device power supply according to claim 2, wherein:
- the AC EMI filter is configured to filter a 115V, 400 Hz power signal from the aircraft's AC power bus; and
- the DC EMI filter is configured to filter a 28 VDC power signal from the aircraft's DC power bus.
4. The aircraft device power supply according to claim 2, wherein:
- the AC EMI filter and DC EMI filter are provided on a common integrated circuit board.
5. The aircraft device power supply according to claim 1, wherein:
- the power factor correction subcircuit comprises a power factor controller chip.
6. The aircraft device power supply according to claim 5, wherein:
- the power factor controller chip controls a boost converter to caused said first voltage to be at least 60 VDC.
7. The aircraft device power supply according to claim 6, wherein:
- the first voltage is between 60-90 VDC; and
- the second voltage is about 12 VDC.
8. The aircraft device power supply according to claim 1, wherein:
- a voltage of the rectified AC power signal is approximately the same as a voltage of the DC signal so that the power factor correction subcircuit receives approximately the same voltage, whether the power supply is connected to the aircraft's AC power bus or to the aircraft's DC power bus.
9. The aircraft device power supply according to claim 1, wherein:
- the first subcircuit is configured to convert the filtered AC power signal to a lower voltage which is approximately equal in magnitude to a voltage supplied by the aircraft's DC power bus.
10. The aircraft device power supply according to claim 1, wherein:
- the AC/DC switchover subcircuit is configured to output only one of the rectified AC power signal and the filtered DC power signal, when the power supply is connected to both the aircraft AC power bus and to the aircraft DC bus.
11. The aircraft device power supply according to claim 10, wherein:
- the AC/DC switchover subcircuit is configured to output only the rectified AC power signal, when the power supply is connected to both the aircraft AC power bus and to the aircraft DC bus.
12. An aircraft-mountable device adapted to be connected to either an aircraft alternating current (AC) power bus or to an aircraft direct current (DC) power bus, the aircraft-mountable device having a power supply comprising:
- a first subcircuit having an input and an output, the first subcircuit configured to accept an AC power signal, convert the AC power signal to a lower voltage, and output a rectified AC power signal, when the power supply is connected to an aircraft AC power bus;
- an AC/DC switchover subcircuit having a first input connected to the output of the first subcircuit and a second input, and further having a switchover output, the AC/DC switchover subcircuit configured to: output the rectified AC power signal, when the power supply is connected to the aircraft AC power bus and not to an aircraft DC power bus; and output a DC signal, when the power supply is connected to the aircraft DC power bus and not to the aircraft AC power bus;
- a power factor correction subcircuit having an input connected to the switchover output, and further having an output, the power factor correction subcircuit configured to correct a power factor of a rectified AC power signal, when the power supply is connected to the aircraft AC power bus, and further configured to output a DC power signal having a first voltage; and
- a DC-DC step-down converter having an input connected to the output of the power factor correction subcircuit, and further having a system voltage output, the DC-DC step-down converter configured to reduce the first voltage to a second voltage lower than said first voltage.
13. The aircraft-mountable device according to claim 12, wherein the device is one from the group consisting of a computer, display panel, communications equipment, a control panel, and a sensor.
14. An aircraft device power supply adapted to be connected to either an aircraft alternating current (AC) power bus or to an aircraft direct current (DC) power bus, and comprising:
- an AC electromagnetic interference (EMI) filter having a first input connectable to an aircraft AC power bus and a first output, the AC EMI filter configured to output a filtered AC power signal, when the power supply is connected to the aircraft AC power bus;
- a DC EMI filter having a second input connectable to an aircraft DC power bus and a second output, the DC EMI filter configured to output a filtered DC power signal, when the power supply is connected to the aircraft DC power bus;
- a first subcircuit having an input connected to the first output of the AC EMI filter and a third output, the first subcircuit configured to accept the filtered AC power signal, convert the filtered AC power signal to a lower voltage, and output a rectified AC power signal, when the power supply is connected to the aircraft AC power bus;
- an AC/DC switchover subcircuit having inputs connected to the second and third outputs, and further having a switchover output, the AC/DC switchover subcircuit configured to: output the rectified AC power signal, when the power supply is connected to the aircraft AC power bus and not to the aircraft DC power bus; and output the filtered DC power signal, when the power supply is connected to the aircraft DC power bus and not to the aircraft AC power bus;
- a power factor correction subcircuit having an input connected to the switchover output, and further having a fourth output, the power factor correction subcircuit configured to correct a power factor of a rectified AC power signal, when the power supply is connected to the aircraft AC power bus, and further configured to output a DC power signal having a first voltage; and
- a DC-DC step-down converter having an input connected to the fourth output, and further having a system voltage output, the DC-DC step-down converter configured to reduce the first voltage to a second voltage lower than said first voltage.
15. The aircraft device power supply according to claim 14, wherein:
- the power factor correction subcircuit comprises a power factor controller chip.
16. The aircraft device power supply according to claim 15, wherein:
- the power factor controller chip controls a boost converter to caused said first voltage to be at least 60 VDC.
17. The aircraft device power supply according to claim 16, wherein:
- the first voltage is between 60-90 VDC; and
- the second voltage is about 12 VDC.
18. The aircraft device power supply according to claim 14, wherein:
- a voltage of the rectified AC power signal is approximately the same as a voltage of the filtered DC power signal so that the power factor correction subcircuit receives approximately the same voltage, whether the power supply is connected to the aircraft's AC power bus or to the aircraft's DC power bus.
19. The aircraft device power supply according to claim 14, wherein:
- the first subcircuit is configured to convert the filtered AC power signal to a lower voltage which is approximately equal in magnitude to a voltage supplied by the aircraft's DC power bus.
20. The aircraft device power supply according to claim 14, wherein:
- the AC EMI filter is configured to filter a 115V, 400 Hz power signal from the aircraft's AC power bus; and
- the DC EMI filter is configured to filter a 28 VDC power signal from the aircraft's DC power bus.
21. The aircraft device power supply according to claim 20, wherein:
- the AC EMI filter and DC EMI filter are provided on a common integrated circuit board.
22. The aircraft device power supply according to claim 14, wherein:
- the AC/DC switchover subcircuit is configured to output only one of the rectified AC power signal and the filtered DC power signal, when the power supply is connected to both the aircraft AC power bus and to the aircraft DC bus.
23. The aircraft device power supply according to claim 22, wherein:
- the AC/DC switchover subcircuit is configured to output only the rectified AC power signal, when the power supply is connected to both the aircraft AC power bus and to the aircraft DC bus.
Type: Application
Filed: May 1, 2007
Publication Date: Nov 1, 2007
Patent Grant number: 7859874
Applicant: Rosemount Aerospace Inc. (Burnsville, MN)
Inventor: David J. Bovitz (Minneapolis, MN)
Application Number: 11/742,941
International Classification: H02H 9/06 (20060101);